Sweet smell of success coming to sewer treatment plant

A breath of fresh - or at least less smelly - air should blow past the Carson City Wastewater Reclamation Plant by September.

A new way to spin water from sludge should bring relief to drivers in the roundabout area of Fifth Street and Edmonds Drive and people living in the River View and River Knolls neighborhoods.

Sewer operations chief Kelvin Ikehara's crew is testing the system and synchronizing the many software programs in a new $5.5 million mechanical sludge dewatering equipment that should be fully operational by the end of April.

The centrifuge, similar in concept to a clothes dryer, will replace the century-old way of drying waste remnants in evaporative ponds.

"We're moving out of the Stone Age and into the new millennium," said Tom Hoffert, the city's utilities operation manager. "This is a major leap."

More important, the sludge drying process is moving from the outdoors to an indoor facility that will contain the notorious odors that permeate the neighborhood.

"On average, the smell produced by the plant will be reduced by 90 percent," Hoffert said.

Since the early 1960s, Carson City has used evaporative ponds to dry out the remnants of waste that emerge from the anaerobic digestion system. The anaerobic system uses bacteria to break down the solid wastes that the sewer brings to the treatment plant.

With city growth, the evaporative pond systems has grown to 22 drying beds covering 14 acres with exposed waste solids. As the waste dries, the smell is released into the air, Hoffert said.

"Instead of ponds to dry the solids, now we're spinning the water out of the solids, which are then transported immediately from the plant," Ikehara said.

The mechanized sludge dewatering equipment consists of two centrifuges. These are cylinders about 16 feet long and 30 inches in diameter that spin while filled with sludge - a mix of waste and water. The spinning removes the water and produces waste cake.

The centrifuge can produce 14 cubic yards of cake a day, enough to handle the waste of 75,000 people, the estimated population of Carson City once all available land is developed.

Carson City first looked at converting from drying beds to a centrifuge in the mid-1990s when frequent odor complaints surfaced from River View and River Knolls.

"When the plant was put here, this was considered way out of town and since then development has surrounded us," Hoffert said.

The utilities department has worked actively on the centrifuge since 1996 but Hoffert said the design and building of such a system takes four years. Construction on the sludge dewatering equipment started in September 1998 and is now in the final tinkering to make sure all the computers interface properly.

The centrifuge system was built with existing revenue with no need to increase sewer rates, Hoffert said.

By the end of the month, no new sludge will be added to the evaporation ponds, but the existing sludge needs to dry out before it can be removed.

"We need the summer heat to dry the solids," Ikehara said.

Hoffert said he is exploring the cost effectiveness of other options to accelerate the drying process. Leaving it to nature will likely take until September or into fall.

"We want to remove the odor as soon as possible," Hoffert said. "We are looking at ways to do it sooner."